Lens module

ABSTRACT

A lens module include a first lens, a second lens, and a distance maintenance member disposed between the first lens and the second lens, the distance maintenance member having a hole for adjusting an amount of light. An inner circumferential surface of the hole includes a plurality of inclined surfaces that are respectively inclined at predetermined angles with respect to an optical axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2012-0151021 filed on Dec. 21, 2012, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens module, and more particularly,to a lens module in which internal reflections such as ghost and flarephenomena are minimized.

2. Description of the Related Art

As levels of performance of portable devices (e.g., portable telephones)are improved, high resolution is required in small cameras installed inportable devices. Thus, small cameras installed in portable devices mayrequire lens modules having increased numbers of lenses.

A lens module including the plurality of lenses may include lenses and alens barrel that accommodates the lenses. The lens module has astructure in which the lenses are sequentially inserted into the lensbarrel to have aligned optical axes.

However, since a lens module may have a structure in which the opticalaxes of the lenses are aligned by the lens barrel, the lenses installedin the lens barrel should have the same diameter or be manufactured tohave common machining errors.

Furthermore, a lens module including a plurality of lenses may cause aflare phenomenon due to internal reflection. As a result, a lens modulemay be deteriorated in terms of resolution.

Thus, development of lens modules which are capable of accuratelyaligning lenses with each other and also reducing a flare phenomenon isrequired.

There are provided Patent Documents 1 and 2 as prior art references inrelation to the present invention. Patent Document 1 discloses a lensbarrel structure in which deviation of focal lengths between lenses.Patent Document 2 discloses a lens structure capable of minimizing asize of a lens barrel.

However, Patent Documents 1 and 2 do not disclose any structure forminimizing ghost and flare phenomena due to internal reflection.

PRIOR ART DOCUMENTS Patent Documents

-   (Patent Document 1) KR2006-081971 A-   (Patent Document 2) JP2011-075682 A

SUMMARY OF THE INVENTION

An aspect of the present invention provides a lens module capable ofeasily aligning lenses and minimizing an occurrence of a flarephenomenon.

According to an aspect of the present invention, there is provided alens module including: a first lens; a second lens; and a distancemaintenance member disposed between the first lens and the second lens,the distance maintenance member having a hole for adjusting an amount oflight, wherein an inner circumferential surface of the hole includes aplurality of inclined surfaces that are respectively inclined atpredetermined angles with respect to an optical axis.

The plurality of inclined surfaces may be discontinuously disposed withregard to one another.

The plurality of inclined surfaces may include: a first inclined surfacehaving a first inclined angle; and a second inclined surface having asecond inclined angle.

The first and second inclined angles may be different from each other.

The lens module may further include a lens barrel that accommodates thefirst lens and the second lens.

The lens barrel may be formed of a material having the same linearexpansion coefficient as those of the first and second lenses.

Each of the first and second lenses may be formed of a plastic material,and the lens barrel may be formed of polyarylate (PAR).

The distance maintenance member may be formed of a nonferrous metal.

According to another aspect of the present invention, there is provideda lens module including: a first lens; a second lens; and a firstdistance maintenance member disposed between the first lens and thesecond lens, the first distance maintenance member having a first holefor adjusting an amount of light; and a second distance maintenancemember disposed between the first lens and the second lens, the seconddistance maintenance member having a second hole for adjusting an amountof light, wherein an inner circumferential surface of the first holeincludes a first inclined surface having a first inclined angle withrespect to an optical axis, and an inner circumferential surface of thesecond hole includes a second inclined surface having a second inclinedangle with respect to the optical axis.

The first and second inclined angles may be different from each other.

The first and second holes may be different in size.

The lens module may further include a lens barrel that accommodates thefirst lens and the second lens.

The lens barrel may be formed of a material having the same linearexpansion coefficient as those of the first and second lenses.

Each of the first and second lenses may be formed of a plastic material,and the lens barrel may be formed of polyarylate (PAR).

Each of the first and second distance maintenance members may be formedof a nonferrous metal.

According to another aspect of the present invention, there is provideda lens module including: a lens barrel; a first lens group coupled tothe lens barrel; a second lens group coupled to the first lens groupwithout in contact with the lens barrel; and a third lens group coupledto the second lens group.

The third lens group may be in contact with the lens barrel.

An inclined surface may be disposed on an outer circumferential surfaceof the third lens group.

The second lens group may include a plurality of lenses.

The lens module may further include a distance maintenance memberdisposed between the second lens group and the third lens group andhaving a hole for adjusting an amount of light.

The distance maintenance member may be formed of a nonferrous metal.

An inner circumferential surface of the hole may include a plurality ofinclined surfaces, each having a predetermined angle with respect to anoptical axis.

The plurality of inclined surfaces may include: a first inclined surfacehaving a first inclined angle; and a second inclined surface having asecond inclined angle.

The first and second inclined angles may be different from each other.

The lens barrel may be formed of a material having the same linearexpansion coefficient as those of the first to third lens groups.

Each of the first to third lenses may be formed of a plastic material,and the lens barrel may be formed of polyarylate (PAR).

The lens module may further include: a first distance maintenance memberdisposed between the second lens group and the third lens group, thefirst distance maintenance member having a first hole for adjusting anamount of light; and a second distance maintenance member disposedbetween the second lens group and the third lens group, the seconddistance maintenance member having a second hole for adjusting theamount of light.

Each of the first and second distance maintenance members may be formedof a nonferrous metal.

An inner circumferential surface of the first hole may include a firstinclined surface having a first inclined angle with respect to anoptical axis, and an inner circumferential surface of the second holemay include a second inclined surface having a second inclined anglewith respect to the optical axis.

The first and second inclined angles may be different from each other.

The first and second holes may be different in size.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view of a lens module according to a first embodiment of thepresent invention;

FIG. 2 is a view illustrating an embodiment of the lens module of FIG.1;

FIG. 3 is a view illustrating a further embodiment of the lens module ofFIG. 1;

FIG. 4 is a view illustrating a further embodiment of the lens module ofFIG. 1;

FIG. 5 is a view of a lens module according to a second embodiment ofthe present invention;

FIG. 6 is a view illustrating an embodiment of the lens module of FIG.5;

FIG. 7 is a view illustrating a further embodiment of the lens module ofFIG. 5;

FIG. 8 is a view of a lens module according to a third embodiment of thepresent invention; and

FIG. 9 is an enlarged view of portion A of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

In following descriptions of the present invention, the terms todescribe the present invention are defined in consideration of featuresof the present invention, and therefore should not be construed that thescope of the invention is limited thereto.

FIG. 1 is a view of a lens module according to a first embodiment of thepresent invention, FIG. 2 is a view illustrating an embodiment of thelens module of FIG. 1, FIG. 3 is a view illustrating a furtherembodiment of the lens module of FIG. 1, FIG. 4 is a view illustrating afurther embodiment of the lens module of FIG. 1, FIG. 5 is a view of alens module according to a second embodiment of the present invention,FIG. 6 is a view illustrating an embodiment of the lens module of FIG.5, FIG. 7 is a view illustrating a further embodiment of the lens moduleof FIG. 5, FIG. 8 is a view of a lens module according to a thirdembodiment of the present invention, and FIG. 9 is an enlarged view ofportion A of FIG. 8.

Hereinafter, a lens module according to a first embodiment of thepresent invention will be described with reference to FIGS. 1 to 4.

A lens module 100 according to the first embodiment may include a firstlens 110, a second lens 120, and a distance maintenance member 160. Inaddition, the lens module 100 may selectively further include a lightshielding member (not shown). Also, the lens module 100 may furtherinclude a plurality of lenses according to a resolution desired to berealized.

The first lens 110 may be manufactured by using glass, a glass mold, athermosetting resin, a thermoplastic resin, or a plastic material. Thefirst lens 110 may generally have a positive refractive index or anegative refractive index. The first lens 110 may be a lens disposedcloser to a subject than the second lens 120 in the lens module 100.

The first lens 110 may include a functional lens part 112 and a flangepart 114. The functional lens part 112 may refract incident lightreflected from the subject. For this, the functional lens part 112 mayhave a concave or convex shape or a meniscus shape. For reference, inthe current embodiment, the functional lens part 112 of the first lens110 may have a meniscus shape, convex toward the second lens 120. Theflange part 114 may be disposed on an edge of the functional lens part112. The flange part 114 may be a portion in contact with another lends(i.e., the second lens 120). Here, the flange part 114 may be coatedwith a light shielding material, or a light shielding film may beattached to the flange part 114. In this case, unnecessary lightincident to the second lens 120 may be blocked by the flange part 114.

The second lens 120 may be manufactured by using glass, a glass mold, athermosetting resin, a thermoplastic resin, or a plastic material. Thesecond lens 120 may generally have a positive refractive index or anegative refractive index. The second lens 120 may be a lens disposedcloser to an image sensor than the first lens 120 in the lens module100.

The second lens 120 may include a functional lens part 122 and a flangepart 124. The functional lens part 122 may refract incident lightreflected from the subject. For this, the functional lens part 122 mayhave a concave or convex shape or a meniscus shape. For reference, inthe current embodiment, the functional lens part 122 of the second lens120 may have a shape that has an inflection point at a point except fora portion (i.e., a center of the lens) crossing an optical axis C-C. Theflange part 124 may be disposed on an edge of the functional lens part122. The flange part 124 may be a portion in contact with another lens(i.e., the first lens 110). Here, the flange part 124 may be coated witha light shielding material, or a light shielding film may be attached tothe flange part 124. In this case, incidence of unnecessary light intothe image sensor may be blocked by the flange part 124.

A distance maintenance member 160 may be disposed between the first lens110 and the second lens 120. The distance maintenance member 160 mayadjust an amount of light incident travelling from the first lens 110 tothe second lens 120. Also, the distance maintenance member may preventunnecessary light incident from the first lens 110 from being incidentto the second lens 120. For this, the distance maintenance member 160may have a hole 162 through which the optical axis C-C passes.

Furthermore, the distance maintenance member 160 may reduce ghost andflare phenomena due to internal reflection of the lens. For this, aplurality of inclined surfaces 164 and 166 may be disposed on an innercircumferential surface of the hole 162 as shown in FIG. 1.

The inclined surfaces 164 and 166 may include a first inclined surface164 and a second inclined surface 166. Here, the first inclined surface164 and the second inclined surface 166 may be discontinuously disposedwith regard to one another. As shown in FIG. 2, at least three inclinedsurfaces 164, 166, and 168 may be provided. In this case, the inclinedsurfaces 164, 166, and 168 may improve the blocking effect of the ghostand flare phenomena. Furthermore, the first and second inclined surfaces164 and 166 may have the same inclined angle with respect to the opticalaxis C-C as shown in FIG. 1. Alternatively, the first and secondinclined surfaces 164 and 166 may have different inclined angles withrespect to the optical axis C-C as shown in FIG. 3. Here, the former mayenable the distance maintenance member 160 to be easily manufactured,and the latter may effectively block occurrence of the ghost and flarephenomena by using the distance maintenance member 160.

The distance maintenance member 160 may be formed of a nonferrous metal.For example, the distance maintenance member 160 may be formed of acopper or aluminum material. In this case, the distance maintenancemember 160 may be easily formed, and also manufacturing costs of thedistance maintenance member 160 may be reduced. For reference, thedistance maintenance member 160 may have a surface coated with a lightshielding material.

The lens module 100 may further include a lens barrel 190. The lensbarrel 190 may be manufactured to have a cylindrical shape toaccommodate the first and second lenses 110 and 120. The lens barrel 190may be coupled to only one lens of the first and second lenses 110 and120. For example, the lens barrel 190 may be coupled to only one lenshaving a relatively large diameter of two lenses. For reference, in thecurrent embodiment, the lens barrel 190 and the second lens 120 arecoupled through mutual contact therebetween.

This coupling structure may be advantageous for mounting a plurality oflenses on the lens barrel 190. That is, since only one lens of theplurality of lenses mounted on the lens barrel 190 is coupled to thelens barrel 190, a press-fitting process for separately press-fittingthe plurality of lenses into the lens barrel 190 may be omitted.Furthermore, since only a few lenses are in contact with the lens barrel190, deformation of the lenses or the lens barrel 190 occurring in thecase that the plurality of lenses are forcibly press-fitted into thelens barrel 190 may be minimized.

The lens barrel 190 and the lenses 110 and 120 may be formed ofmaterials having the same linear expansion coefficient. For example, thelens barrel 190 may be formed of a polyarylate (PAR) material. Here,since the PAR has substantially the same linear expansion coefficient asthe lenses 110 and 120 formed of plastic, the PAR may effectively bufferthe contraction and expansion of the lens due to a temperature change inthe surrounding environment.

As described above, the lens module may reduce the occurrence of theghost and flare phenomena due to the internal reflection of the lensthrough the distance maintenance member 160 having the plurality ofinclined surfaces.

In addition, since the lenses 110 and the 120 and the lens barrel 190 ofthe lens module 100 are formed of the materials having the same linearexpansion coefficient, a phenomenon in which an alignment positionbetween the lenses is twisted while the lenses are expanded orcontracted at a high or a low temperature may be minimized.

Hereinafter, a lens module according to another embodiment of thepresent invention will be described. In the following description ofanother embodiment, the same components as the first embodiment areindicated by the same reference numerals as the first embodiment, andthus detailed descriptions with respect to the components will beomitted.

A lens module according to a second embodiment will be described withreference to FIGS. 5 to 7.

A lens module 100 according to the current embodiment may bedistinguishable from the lens module 100 according to the firstembodiment in terms of configurations of distance maintenance members160 and 170. For reference, the lens module 100 according to the currentembodiment may be distinguished from the lens module 100 according tothe first embodiment in that the plurality of distance maintenancemembers 160 and 170 are provided.

In the current embodiment, the distance maintenance members 160 and 170may be provided in plural. That is, as shown in FIG. 5, the distancemaintenance members 160 and 170 may include first and second distancemaintenance members 160 and 170. A first hole 162 may be formed in thefirst distance maintenance member 160, and a second hole 172 may beformed in the second distance maintenance member 170. Here, the firstand second holes 162 and 172 may have the same size or different sizes.Here, the former may allow the distance maintenance members 160 and 170to be easily manufactured, and the latter may effectively prevent theghost and flare phenomena from occurring by using the distancemaintenance members 160 and 170. For reference, each of the first andsecond holes 162 and 172 may have a cross-sectional area graduallyincreasing from a first lens 110 toward a second lens 120.

A first inclined surface 164 may be disposed on an inner circumferentialsurface of the first hole 162. The first inclined surface 164 may beinclined at a predetermined angle with respect to an optical axis C-C.Here, the inclined angle of the first inclined surface 164 may bechanged according to a size of the lens and a disposition of the firstdistance maintenance member 160.

Similarly, a second inclined surface 174 may be disposed on an innercircumferential surface of the second hole 172. The second inclinedsurface 174 may be inclined at a predetermined angle with respect to theoptical axis C-C. Here, the inclined angle of the second inclinedsurface 174 may be changed according to a size of the lens and adisposed position of the second distance maintenance member 170. Also,the second inclined surface 174 may have the same inclined angle as thatof the first inclined surface 164 or have an inclined angle differentfrom that of the first inclined surface 164.

As shown in FIG. 7, the lens module 100 according to the currentembodiment may further include a lens barrel 190 as occasion demands.

In an embodiment of the current embodiment, as shown in FIG. 6, thedistance maintenance members may include three distance maintenancemembers 160, 170, and 180. In detail, the distance maintenance membersmay include a first distance maintenance member 160, a second distancemaintenance member 170, and a third distance maintenance member 180.

A first hole 162 having a first size may be formed in the first distancemaintenance member 160. Also, the first inclined surface 164 may bedisposed on an inner circumferential surface of the first hole 162. Asecond hole 172 having a second size may be formed in the seconddistance maintenance member 170. Also, the second inclined surface 174may be disposed on an inner circumferential surface of the second hole172. Similarly, a third hole 182 having a third size may be formed inthe third distance maintenance member 180. Also, a third inclinedsurface 184 may be disposed on an inner circumferential surface of thethird hole 182. Here, the first hole 162, the second hole 174, and thethird hole 184 may be different in size. Furthermore, the first inclinedsurface 164, the second inclined surface 174, and the third inclinedsurface 184 may have the same inclined angle or have inclined anglesdifferent from one another. Also, the first and second inclined surfaces164 and 174 or the second and third inclined surfaces 174 and 184 mayhave inclination directions different from each other. For example, thefirst and second inclined surfaces 164 and 184 may have the sameinclined angle, but the first and second inclined surfaces 164 and 174may have inclined angles and directions different from each other.

The distance maintenance members 160, 170, and 180 according to thecurrent embodiment may be manufactured in a thin film shape such as afilm. Also, the distance maintenance members 160, 170, and 180 may beindependently manufactured, and then the respective distance maintenancemembers 160, 170, and 180 may be integrally bonded or coupled to eachother.

The lens module 100 may be advantageous for mounting the distancemaintenance members 160, 170, and 180, each having a complex shape,between the lenses 120 and 130. That is, since the distance maintenancemembers 160, 170, and 180 are separated for each section havingdifferent characteristics, the inner circumferential surfaces of theholes 162, 172, and 182 may have various shapes. Thus, according to thecurrent embodiment, the blocking effect of the ghost and flare phenomenamay be maximized through the inclined surfaces 164, 174, and 184 of thedistance maintenance members 160, 170, and 180.

Hereinafter, a lens module according to a third embodiment of thepresent invention will be described with reference to FIGS. 8 to 9.

A lens module 100 according to the current embodiment may include aplurality of lens groups G1, G2, and G3 as shown in FIG. 8. Forreference, the lens module 100 may include a first lens group G1, asecond lens group G2, and a third lens group G3. In addition, the lensgroup 100 may include the above-described distance maintenance member160.

The first lens group G1 may be a lens group disposed closest to asubject in the lens module 100. Also, the first lens group G1 mayinclude at least one lens. For reference, the first lens group G1 mayinclude a first lens 100 disposed closest to the subject. However, thefirst lens group G1 may only not include the first lens 110. Forexample, the first lens group G1 may include other lenses in addition tothe first lens 110.

The first lens group G1 may be coupled to a lens barrel 190. Forreference, the lens of the first lens group G1 may be in contact withthe lens barrel 190 and aligned with an optical axis. That is, top andside surfaces of the first lens 110 may be in contact with an innercircumferential surface of the lens barrel 190, and then an optical axisof the first lens 110 may be aligned with the optical axis of the lensbarrel 190.

The second lens group G2 may be disposed between the first lens group G1and the third lens group G3. Also, the second lens group G2 may includeat least one lens. For reference, the second lens group G2 may include asecond lens 120, a third lens 130, and a fourth lens 140.

The second lens group G2 may be aligned by the first lens group G1. Forreference, the lenses 120, 130, and 140 of the second lens group G2 maybe coupled to the first lens 110 of the first lens group G1 and alignedwith the optical axis of the first lens group G1. For this, the firstand second lens groups G1 and G2 may have structures that are capable ofbeing coupled and aligned with each other. For example, the first lensgroup G1 may have a conical surface, a protrusion, or a groove therein.Also, the second lens group G2 may have a shape corresponding to that ofthe conical surface, protrusion, or groove of the first lens group G1.

The second lens group G2 may not be in contact with the lens barrel 190.That is, the second lens group G2 may be in contact with the first lensgroup G1, but not be in contact with the lens barrel 190. In this case,the second lens group G2 including a plurality of lenses may be easilymounted in the lens barrel 190. Also, since the second lens group G2 iscoupled to the first lens group G1 without being in contact with thelens barrel 190, the optical axis of the second lens group G2 may bealways aligned with that of the first lens group G1.

The third lens group G3 may be disposed closest to an image sensor.Also, the third lens group G3 may include a plurality of lenses. Forreference, the third lens group G3 may include a fifth lens 150 disposedclosest to the image sensor. Also, the third lens group G3 may furtherinclude an IR filter, blocking infrared rays, as occasion demands.

The third lens group G3 may be in contact with the lens barrel 190. Forreference, the third lens group G3 may be coupled to the lens barrel 190to prevent the second lens group G2 from being separated from the lensbarrel 190.

A vertical surface 156 and an inclined surface 158 may be disposed on aside surface of the fifth lens 150 constituting the third lens group G3as shown in FIG. 9. Here, the vertical surface 156 may increase an areaof friction between the fifth lens 150 and the lens barrel 190 toimprove coupling force between the fifth lens 150 and the lens barrel190. On the other hand, the inclined surface 158 may enable the fifthlens 150 to be easily press-fitted into the lens barrel 190 as well asto easily separate the fifth lens 150 from a mold for molding the lens.

For reference, although the vertical surface 156 and the inclinedsurface 158 are only disposed on the fifth lens 150 of the third lensgroup G3 in the current embodiment, the present invention is not limitedthereto. For example, a vertical surface and an inclined surface may bedisposed on side surfaces of the lenses constituting the first andsecond lens groups G1 and G2.

The distance maintenance member 160 may be disposed between the secondlens group G2 and the third lens group G3. A plurality of inclinedsurfaces 164 and 166 may be disposed on an inner circumferential surfaceof the distance maintenance member 160. As described above, the distancemaintenance member 160 may effectively reduce the ghost and flarephenomena due to the internal reflection of the lens.

Although the distance maintenance member 160 is disposed between thesecond lens group G2 and the third lens group G3 in FIG. 8, the presentinvention is not limited thereto. For example, the distance maintenancemember 160 may be disposed between the first lens group G1 and thesecond lens group G2 or between the lenses constituting the second lensgroup G2.

The present invention may effectively reduce the ghost and flarephenomena due to the internal reflection of the lens to improveresolution of the lens module.

In addition, the contact area between the lens barrel and the lens maybe minimized to reduce the deformation of the lens barrel and the lensdue to the press-fitting between the lens barrel and the lens.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A lens module comprising: a first lens; a secondlens; and a distance maintenance member disposed between the first lensand the second lens, the distance maintenance member having a hole foradjusting an amount of light, wherein an inner circumferential surfaceof the hole comprises a plurality of inclined surfaces that arerespectively inclined at predetermined angles with respect to an opticalaxis.
 2. The lens module of claim 1, wherein the plurality of inclinedsurfaces are discontinuously disposed with regard to one another.
 3. Thelens module of claim 1, wherein the plurality of inclined surfacescomprise: a first inclined surface having a first inclined angle; and asecond inclined surface having a second inclined angle.
 4. The lensmodule of claim 3, wherein the first and second inclined angles aredifferent from each other.
 5. The lens module of claim 1, furthercomprising a lens barrel that accommodates the first lens and the secondlens.
 6. The lens module of claim 5, wherein the lens barrel is formedof a material having the same linear expansion coefficient as those ofthe first and second lenses.
 7. The lens module of claim 6, wherein eachof the first and second lenses is formed of a plastic material, and thelens barrel is formed of polyarylate (PAR).
 8. The lens module of claim1, wherein the distance maintenance member is formed of a nonferrousmetal.
 9. A lens module comprising: a first lens; a second lens; and afirst distance maintenance member disposed between the first lens andthe second lens, the first distance maintenance member having a firsthole for adjusting an amount of light; and a second distance maintenancemember disposed between the first lens and the second lens, the seconddistance maintenance member having a second hole for adjusting an amountof light, wherein an inner circumferential surface of the first holecomprises a first inclined surface having a first inclined angle withrespect to an optical axis, and an inner circumferential surface of thesecond hole comprises a second inclined surface having a second inclinedangle with respect to the optical axis.
 10. The lens module of claim 9,wherein the first and second inclined angles are different from eachother.
 11. The lens module of claim 9, wherein the first and secondholes are different in size.
 12. The lens module of claim 9, furthercomprising a lens barrel that accommodates the first lens and the secondlens.
 13. The lens module of claim 12, wherein the lens barrel is formedof a material having the same linear expansion coefficient as those ofthe first and second lenses.
 14. The lens module of claim 13, whereineach of the first and second lenses is formed of a plastic material, andthe lens barrel is formed of polyarylate (PAR).
 15. The lens module ofclaim 9, wherein each of the first and second distance maintenancemembers is formed of a nonferrous metal.
 16. A lens module comprising: alens barrel; a first lens group coupled to the lens barrel; a secondlens group coupled to the first lens group without in contact with thelens barrel; and a third lens group coupled to the second lens group.17. The lens module of claim 16, wherein the third lens group is incontact with the lens barrel.
 18. The lens module of claim 16, whereinan inclined surface is disposed on an outer circumferential surface ofthe third lens group.
 19. The lens module of claim 16, wherein thesecond lens group comprises a plurality of lenses.
 20. The lens moduleof claim 16, further comprising a distance maintenance member disposedbetween the second lens group and the third lens group and having a holefor adjusting an amount of light.
 21. The lens module of claim 20,wherein the distance maintenance member is formed of a nonferrous metal.22. The lens module of claim 20, wherein an inner circumferentialsurface of the hole comprises a plurality of inclined surfaces, eachhaving a predetermined angle with respect to an optical axis.
 23. Thelens module of claim 22, wherein the plurality of inclined surfacescomprise: a first inclined surface having a first inclined angle; and asecond inclined surface having a second inclined angle.
 24. The lensmodule of claim 23, wherein the first and second inclined angles aredifferent from each other.
 25. The lens module of claim 16, wherein thelens barrel is formed of a material having the same linear expansioncoefficient as those of the first to third lens groups.
 26. The lensmodule of claim 25, wherein each of the first to third lenses is formedof a plastic material, and the lens barrel is formed of polyarylate(PAR).
 27. The lens module of claim 16, further comprising: a firstdistance maintenance member disposed between the second lens group andthe third lens group, the first distance maintenance member having afirst hole for adjusting an amount of light; and a second distancemaintenance member disposed between the second lens group and the thirdlens group, the second distance maintenance member having a second holefor adjusting the amount of light.
 28. The lens module of claim 27,wherein each of the first and second distance maintenance members isformed of a nonferrous metal.
 29. The lens module of claim 27, whereinan inner circumferential surface of the first hole comprises a firstinclined surface having a first inclined angle with respect to anoptical axis, and an inner circumferential surface of the second holecomprises a second inclined surface having a second inclined angle withrespect to the optical axis.
 30. The lens module of claim 29, whereinthe first and second inclined angles are different from each other. 31.The lens module of claim 29, wherein the first and second holes aredifferent in size.